If you got a subwoofer you can check to see if a small piece of metal got attracted to it... Toshiba had a tech alert when they started seeing units being returned for repair due to a staple or other small item getting drawn up by the subwoofer and making a crackling noise.
If the front speakers not being detected... what method are you using to confirm this. I can't remember windows ever "detecting" speakers unless they were USB. In the device manager is a system speaker item, but that really has more to do with the sound chip rather than the speaker itself.